1. Field
The present disclosure relates to a mobile operating environment, and more particularly, to selectively maintaining data packet session continuity when changing coverage areas for voice sessions that use different radio access technologies.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-signal-out or a multiple-in-multiple-out (MIMO) system.
Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) cell phone technologies. UTRAN, short for UMTS Terrestrial Radio Access Network, is a collective term for the Node-B's and Radio Network Controllers which make up the UMTS radio access network. This communications network can carry many traffic types from real-time Circuit Switched to IP based Packet Switched. The UTRAN allows connectivity between the UE (user equipment) and the core network. The UTRAN contains the base stations, which are called Node Bs, and Radio Network Controllers (RNC). The RNC provides control functionalities for one or more Node Bs. A Node B and an RNC can be the same device, although typical implementations have a separate RNC located in a central office serving multiple Node B's. Despite the fact that they do not have to be physically separated, there is a logical interface between them known as the Iub. The RNC and its corresponding Node Bs are called the Radio Network Subsystem (RNS). There can be more than one RNS present in an UTRAN.
CDMA2000 (also known as IMT Multi Carrier (IMT MC)) is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B. All are approved radio interfaces for the ITU's IMT-2000. CDMA2000 has a relatively long technical history and is backward-compatible with its previous 2G iteration IS-95 (cdmaOne).
CDMA2000 1X (IS-2000), also known as 1× and 1×RTT, is the core CDMA2000 wireless air interface standard. The designation “1×”, meaning 1 times Radio Transmission Technology, indicates the same RF bandwidth as IS-95: a duplex pair of 1.25 MHz radio channels. 1×RTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link, orthogonal to (in quadrature with) the original set of 64. The 1X standard supports packet data speeds of up to 153 kbps with real world data transmission averaging 60-100 kbps in most commercial applications. IMT-2000 also made changes to the data link layer for the greater use of data services, including medium and link access control protocols and Quality of Service (QoS). The IS-95 data link layer only provided “best effort delivery” for data and circuit switched channel for voice (i.e., a voice frame once every 20 ms).
CDMA2000 1XEV-DO (Evolution-Data Optimized), often abbreviated as EV-DO or EV, is a telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. It uses multiplexing techniques including code division multiple access (CDMA) as well as time division multiple access (TDMA) to maximize both individual user's throughput and the overall system throughput. It is standardized by 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and has been adopted by many mobile phone service providers around the world, particularly those previously employing CDMA networks.
3GPP LTE (Long Term Evolution) is the name given to a project within the 3rd Generation Partnership Project (3GPP) to improve the UMTS mobile phone standard to cope with future requirements. Goals include improving efficiency, lowering costs, improving services, making use of new spectrum opportunities, and better integration with other open standards. The LTE system is described in the Evolved UTRA (EUTRA) and Evolved UTRAN (EUTRAN) series of specifications.
Dual mode (or multimode) mobiles refer to mobile phones that are compatible with more than one form of data transmission or network, as contrasted with single-mode mobiles. For instance, a dual-mode phone can be a telephone which uses more than one technique for sending and receiving voice and data. This could be for wireless mobile phones or for wired phones.
In one aspect, the dual mode can refer to network compatibility, such as mobile phones containing two types of cellular radios for voice and data. These phones include combination of GSM and CDMA technology. They can be used as a GSM or CDMA phone according to user preference. These handsets are also called global phones and are essentially two phones in one device. For this particular example of a dual mode cdma2000 and GSM phone, there are two possibilities, either two cards (R-UIM and SIM) or one card (SIM-only) where the R-UIM information is stored in the Mobile Equipment (handset shell).
Another kind of dual mode or multimode mobiles can refer to User Equipment (UEs) that have more than one receiver, more than one transmitter, or more than one transceiver enabling simultaneous operations in two different modes. For example, voice and data sessions can be performed separately and simultaneously. Alternatively, a secondary transceiver can be used to acquire new service or maintain continuity of a current session while using a primary transceiver.
Situations can arise wherein a multimode UE receives service from a Radio Access Network (RAN) that uses a Radio Access Technology (RAT) that can support both a voice session and a data session. In moving to a coverage area of a different RAN, acquiring and establishing connections on two different RATs can be required in order to continue the voice and data session, each imposing differing amounts of delays for achieving a simultaneous handoff without losing session continuity. Lengthy delays can significantly degrade user equipment and Quality of Service (QoS).